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Abstract:

The present invention relates to a technique which can make a backlight
used in a liquid crystal display device thin and light-weighted. The
present invention provides a liquid crystal display device which includes
a display panel and a backlight which is arranged behind the display
panel, wherein the backlight includes a film-like light guide member, a
film-like light semi-transmissive member which is adhered to a first
surface of the light guide member which faces the display panel in an
opposed manner, a film-like reflective member which is adhered to a back
surface of the light guide member opposite to the first surface, and a
spot light source which is arranged at a position of the light guide
member at which light is incident on the light guide member from the
first surface or the back surface, and a refractive index of the light
semi-transmissive member is set smaller than a refractive index of the
light guide member.

Claims:

1. A display device comprising: a display panel: and a backlight which is
arranged behind the display panel, wherein the display panel adheres a
polarizer to a surface thereof which faces the backlight in an opposed
manner and a back surface thereof opposite to the surface, and the
backlight includes a film-like light guide member, a film-like light
polarization reflective member which is adhered to a first surface of the
light guide member which faces the display panel in an opposed manner, a
film-like reflective member which is adhered to a back surface of the
light guide member opposite to the first surface, and a spot light source
which is arranged at a position of the light guide member at which light
is incident on the light guide member from the first surface or the back
surface, wherein a transmission axis of the polarization reflective
member is arranged in the same direction as a transmission axis of the
polarizer which is adhered to the surface of the display panel which
faces the backlight in an opposed manner.

2. A display device according to claim 1, wherein the backlight includes
a reflector which is arranged in the direction that the spot light source
radiates the light in the film surface direction of the light guide
member, and allows the light radiated from the spot light source to be
incident on the light guide member by reflecting the light.

3. A display device according to claim 1, wherein the light
semi-transmissive member or the polarization reflective member changes a
ratio of transmissivity and reflectance of light which propagates in the
light guide member corresponding to a distance from a position at which
the light of the light guide member is incident.

4. A display device according to claim 1, wherein a plurality of through
holes are formed in a plurality of portions of the light
semi-transmissive member or the polarization reflective member, and the
distribution density of the through holes is changed corresponding to a
distance from a position at which the light of the light guide member is
incident.

5. A display device according to claim 1, wherein the reflective member
changes reflectance thereof corresponding to a distance from a position
at which the light of the light guide member is incident.

6. A display device according to claim 1, wherein the reflective member
has an irregular reflection pattern formed of a concave shape or a convex
shape at a plurality of portions of a surface of the reflective member
which is brought into close contact with the light guide member, and the
distribution density of the irregular reflection pattern is changed
corresponding to a distance from a position at which light of the light
guide member is incident.

7. A planar light source device comprising: a light source; and a
film-like light guide member, wherein the light source includes a
film-like incident-light adjusting member which is arranged in the
direction at which light is radiated in the direction perpendicular to a
film surface of the light guide member, and changes the incident
direction of light to the light guide member is changed in the
propagation direction of light in the light guide member between a region
on which the light is incident and a surface to which light of the light
source is radiated, and the incident-light adjusting member has one, two
or more projections on a surface side which faces the light guide member
in an opposed manner, and distal end surfaces of the projections are
brought into close contact with the light guide member.

8. A planar light source device according to claim 7, wherein a
radiation-light adjusting member which adjusts a radiation angle of the
light from the radiation surface is provided to a radiation surface of
the light of the light guide member.

9. A planar light source device according to claim 8, wherein a
reflective member is provided to a back surface of the light guide member
opposite to a surface on which the incident-light adjusting member is
arranged and to a region which is overlapped to the incident-light
adjusting member.

10. A planar light source device according to claim 8, wherein a
projection of the incident-light adjusting member is a columnar
projection having a curved bottom surface.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a Continuation of U.S. application Ser.
No. 11/634,262 filed on Dec. 6, 2006. Priority is claimed from U.S.
application Ser. No. 11/634,262 filed on Dec. 6, 2006, which claims
priority from Japanese application 2005-352167 filed on Dec. 6, 2005, the
content of which is hereby incorporated by reference into this
application.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a display device and a planar
light source device, and more particularly to a technique which is
effectively applicable to a planar light source device which radiates
light propagated through a light guide plate and a display device which
uses the planar light source device.

[0004] 2. Description of the Related Arts

[0005] Conventionally, as a display of a mobile phone or a notebook-type
PC (Personal Computer) or the like, a liquid crystal display device (a
liquid crystal display unit) having a liquid crystal display panel is
used.

[0006] The liquid crystal display device is roughly classified into a
transmissive-type liquid crystal display device which displays an image
(a video) by arranging a backlight (a light source) behind the liquid
crystal display panel and radiating light from the light source to the
liquid crystal display panel and allowing the light to pass through the
liquid crystal display panel, and a reflective-type liquid crystal
display device which displays an image (a video) by reflecting light from
outside a display device on a liquid crystal display panel.

[0007] Further, the backlight of the transmissive-type liquid crystal
display device is roughly classified into, for example, a direct-type
backlight which arranges a light source such as a fluorescent tube in a
region which is overlapped to a display region of a liquid crystal
display panel, and an edge-light-type (also referred to as a
side-light-type) backlight which arranges a light guide plate in a region
which is overlapped to a display region of a liquid crystal display panel
and arranges a light source on an end portion of the light guide plate.

[0008] The edge-light-type backlight is a backlight which radiates light
to the liquid crystal display panel by propagating light from the light
source which is arranged on the end portion of the light guide plate in
the inside of the light guide plate, directing the light in the direction
toward the liquid crystal display panel by a reflective portion formed on
a back surface of the light guide plate and by diffusing the light using
a diffusion plate. The edge-light-type backlight can reduce a thickness
thereof compared to a thickness of the direct-type backlight.
Accordingly, the liquid crystal'display device having the edge-light-type
backlight has been often used in a display of a mobile phone or a
notebook-type PC.

[0009] Further, with respect to the edge-light-type backlight, to
uniformly radiate light to the display region of the liquid crystal
display panel, there has been known a backlight which uses a combination
of a light guide plate to which a shape which efficiently reflects the
propagating light (for example, grooves) is applied and a reflective
sheet (for example, see Japanese Patent Laid-open No. 11599/2005 (patent
document 1)).

[0010] Further, with respect to the edge-light-type backlight, to achieve
the reduction of thickness of the backlight, for example, there has been
known a backlight which is constituted of a light guide body layer (a
light guide plate), a reflection layer (a reflective portion) and a
diffusion layer (a diffusion plate) as the integral structure, wherein
each layer is formed of a thin film sheet (for example, see Japanese
Patent Laid-open Hei 08-152526 (patent document 2)).

SUMMARY OF THE INVENTION

[0011] However, for example, in the backlight described in the
above-mentioned patent document 1, the reflection grooves or the like are
formed in the light guide plate and hence, a gap is defined between the
reflective sheets and light infiltrates into the gap. Further, due to the
formation of the grooves, there exists light which reflects or refracts
at an angle which does not contribute to the front face brightness.
Accordingly, there has been a drawback that loss of light is increased.
Further, in general, the light guide plate is often formed by injection
molding and hence, there has been a drawback that it is difficult to form
the light guide plate into a shape as designed from a viewpoint of
forming accuracy.

[0012] Further, for example, the backlight described in the
above-mentioned patent document 2 makes use of the generation of a total
reflection on an interface between the sheets by combining thin film
sheets having different refractive indexes. However, no consideration has
been taken by the patent document 2 with respect to an incident angle of
light when the light is incident on the light guide body layer from the
light source. Accordingly, for example, the light which is incident on
the light guide plate at a small incident angle which does not generate
the total reflection becomes dominant thus giving rise to a drawback that
light cannot be effectively radiated into the inside of a display region
of the liquid crystal display panel.

[0013] Further, in the liquid crystal display device (the liquid crystal
display unit) which is used in a mobile phone or the like, recently, to
achieve the reduction of weight of the liquid crystal display device, for
example, a spot light source such as an LED (Light Emitting Diode) is
used as the light source of the backlight. However, the backlight
described in the patent document 2 premises the use of a linear light
source such as a fluorescent tube as the light source. Accordingly, for
example, when the spot light source such as the LED is used, there has
been a drawback that it is difficult to make the brightness distribution
of the light which is radiated into the inside of the display region of
the liquid crystal display panel.

[0014] Accordingly, it is an object of the present invention to provide a
technique which can achieve the reduction of thickness and the reduction
of weight of a backlight used in a liquid crystal display device, for
example.

[0015] It is another object of the present invention to provide a
technique which can achieve the reduction of thickness, the reduction of
weight of a backlight used in a liquid crystal display device, and the
increase of brightness of the liquid crystal display device, for example.

[0016] The above-mentioned and other objects and novel features of the
present invention will become apparent from the description of this
specification and attached drawings.

[0017] To explain the summary of typical inventions among the inventions
disclosed in this specification, they are as follows.

[0018] (1) In a display device which includes a display panel and a
backlight which is arranged behind the display panel, the backlight
includes a film-like light guide member, a film-like light
semi-transmissive member which is adhered to a first surface of the light
guide member which faces the display panel in an opposed manner, a
film-like reflective member which is adhered to a back surface of the
light guide member opposite to the first surface, and a spot light source
which is arranged at a position of the light guide member at which light
is incident on the light guide member from the first surface or the back
surface, wherein a refractive index of the light semi-transmissive member
is set smaller than a refractive index of the light guide member.

[0019] (2) In a display device which includes a display panel and a
backlight which is arranged behind the display panel, the display panel
adheres a polarizer on a surface thereof which faces the backlight in an
opposed manner and a back surface thereof opposite to the surface, and
the backlight includes a film-like light guide member, a film-like
polarization reflective member which is adhered to a first surface of the
light guide member which faces the display panel in an opposed manner, a
film-like reflective member which is adhered to a back surface of the
light guide member opposite to the first surface, and a spot light source
which is arranged at a position of the light guide member at which light
is incident on the light guide member from the first surface or the back
surface, wherein a transmission axis of the polarization reflective
member is directed in the same direction as a transmission axis of the
polarizer which is adhered to the surface of the display panel which
faces the backlight in an opposed manner.

[0020] (3) In the display device having the above-mentioned means (1) or
(2), the backlight includes a reflector which is arranged in the
direction that the spot light source radiates the light in the film
surface direction of the light guide member and allows the light radiated
from the spot light source to be incident on the light guide member by
reflecting the light.

[0021] (4) In the display device having the above-mentioned means (1) or
(2), the light semi-transmissive member or the polarization reflective
member changes a ratio of transmissivity and reflectance of light which
propagates in the light guide member corresponding to a distance from a
position at which the light of the light guide member is incident.

[0022] (5) In the display device having the above-mentioned means (1) or
(2), a plurality of through holes are formed in a plurality of portions
of the light semi-transmissive member or the polarization reflective
member, and the distribution density of the through holes is changed
corresponding to a distance from a position at which the light of the
light guide member is incident.

[0023] (6) In the display device having the above-mentioned means (1) or
(2), the reflective member changes reflectance thereof corresponding to a
distance from a position at which the light of the light guide member is
incident.

[0024] (7) In the display device having the above-mentioned means (1) or
(2), the reflective member has an irregular reflection pattern formed of
a concave shape or a convex shape at a plurality of portions of a surface
of the reflective member which is brought into close contact with the
light guide member, and the distribution density of the'irregular
reflection pattern is changed corresponding to a distance from a position
at which the light of the light guide member is incident.

[0025] (8) In a planar light source device having a light source and a
film-like light guide member, the light source includes a film-like
incident-light adjusting member which is arranged in the direction that
light is radiated in the direction perpendicular to a film surface of the
light guide member and changes the incident direction of light to the
light guide member to the propagation direction of light of the light
guide member between a region of the light guide member which allows
light to be incident thereon and a surface of the light source from which
light is radiated, and the incident-light adjusting member has one, two
or more projections on a surface side thereof which faces the light guide
member in an opposed manner, and distal end surfaces of the projections
are brought into close contact with the light guide member.

[0026] (9) In the planar light source device having the above-mentioned
means (8), a light radiation surface of the light guide member has a
radiation light adjusting member which adjusts a radiation angle of the
light from the light radiation surface.

[0027] (10) In the planar light source device having the above-mentioned
means (8) or (9), the light guide member includes a reflective member on
a back surface thereof opposite to a surface thereof on which the
incident-light adjusting member is arranged and in a region thereof which
is overlapped to the incident-light adjusting member.

[0028] (11) In any one of the planar light source devices having the
above-mentioned means (8) to (10), the projections of the incident-light
adjusting member are columnar projections each of which has a curved
bottom surface.

[0029] (12) In a display device which includes a display panel and a
backlight which is arranged behind the display panel, the backlight is
formed of the planar light source device included in any one of the
planar light source devices having the above-mentioned means (8) to (11).

[0030] The display device of the present invention adopts the constitution
in which the portion which propagates the light of the backlight is
integrally configured such that, as shown in the above-mentioned means
(1), the film-like light guide member is sandwiched between the film-like
light semi-transmissive member and the film-like reflective member. Here,
each member is integrally formed by adhering film-like formed members
having a thickness of 0.25 mm or less to each other, for example. Due to
such a constitution, the light guide plate can be made thin and
light-weighted. Further, by adopting the integral constitution formed of
a film-like light guide member, a semi-transmissive member and a
reflective member, light which is incident on the light guide member
propagates through the light guide member while repeating the reflection
between the semi-transmissive member and the reflective member with high
efficiency. Accordingly, loss of the light which propagates through the
light guide member is decreased thus increasing the brightness of the
light radiated to the display region of the display panel.

[0031] Further, in the display device of the present invention, the
constitution of the portion which propagates the light of the backlight
may adopt a film-like polarization reflective member in place of the
semi-transmissive member as in the case of the above-mentioned means (2).

[0032] Here, by adopting the above-mentioned constitution of the means
(3), the loss of light can be reduced and hence, the brightness of light
which is radiated to the display region of the display panel can be
increased. Here, it is preferable that the above-mentioned reflector has
a reflective surface having a convex shape in the direction toward the
spot light source, for example.

[0033] Further, by constituting the light semi-transmissive member or the
polarization reflective member as in the case of the above-mentioned
means (4), it is possible to make the in-plane brightness of the light
radiated to the display region of the display panel uniform. Here, in
place of changing the ratio between the transmissivity and the
reflectance of the light semi-transmissive member or the polarization
reflective member as in the case of the above-mentioned means (4), a
plurality of through holes may be formed in the light semi-transmissive
member or the polarization reflective member by changing the distribution
density of the through holes as in the case of the above-mentioned means
(5).

[0034] Further, in place of changing the ratio between the transmissivity
and the reflectance of the light semi-transmissive member or the
polarization reflective member as in the case of the above-mentioned
means (4), the reflectance of the reflective member may be changed as in
the case of the above-mentioned means (6). Here, in place of changing the
reflectance of the reflective member as in the case of the
above-mentioned means (6), a plurality of irregular reflection patterns
may be provided to a surface of the reflective member which is laminated
to the light guide member while changing the distribution density of the
irregular reflection patterns as in the case of the above-mentioned means
(7).

[0035] Further, when the light radiated from the spot light source is
directed toward the film surface of the light guide member as in the case
of the above-mentioned means (3), even when the light is reflected on the
reflector, there may be a case that among the light which is incident on
the light guide member, the light whose incident angle does not exceed a
critical angle becomes dominant. With respect to the light which is
incident with the angle which does not exceed the critical angle and
propagates through the light guide member, there is no possibility that
such a light is totally reflected on an interface with the light
semi-transmissive member or the polarization reflective member or an
interface with the reflective member. Accordingly, the light leaks to the
outside of the light guide member on each interface, and the light does
not propagate through the inside of the light guide member.

[0036] To overcome such a drawback, for example, as in the case of the
above-mentioned means (8), it is desirable to use the planar light source
device which is arranged to radiate the light in the direction
perpendicular to the film surface of the light guide member as the spot
light source. Here, the above-mentioned incident light adjusting member
may be arranged between the spot light source and the light guide member.
Due to such a constitution, the light of the spot light source which is
radiated in the direction perpendicular to the film surface of the light
guide member is allowed to be incident on the light guide member while
converting the incident angle thereof into an angle which exceeds the
critical angle in the inside of the light guide member using the incident
light adjusting member. Accordingly, it is possible to allow the light of
the spot light source to be effectively incident on the light guide
member thus acquiring the higher brightness uniformity.

[0037] Further, for example, as in the Case of the above-mentioned means
(9), the radiation light adjusting member which adjusts the radiation
angle of the light from the radiation surface may be provided to the
radiation surface of light of the light guide member. The radiation light
adjusting member may be constituted in the same manner as the
above-mentioned incident light adjusting member, for example. Due to such
a constitution, for example, even when the light guide member is not
sandwiched between the light semi-transmissive member and the reflective
member, it is possible to radiate the light which is incident on the
light guide member in a planar shape while propagating the light through
the light guide member.

[0038] Further, by providing the reflective member as in the case of the
above-mentioned means (10), it is possible to allow the light which is
radiated to the outside of light guide member to be reflected on the
above-mentioned reflective portion without making the incident angle
exceed the critical angle using the incident light adjusting member thus
allowing the light to be incident on the light guide member again.

[0039] Here, by adopting the constitution of the means (11), it is
possible to propagate the light of the spot light source in a spreading
manner in the inside of the light guide member.

[0040] In this manner, with the provision of the planer light source
device having any one of the above-mentioned means (8) to means (11), it
is possible to allow the light of the spot light source to be effectively
incident on and to propagate through the light guide member thus
acquiring the high brightness uniformity. Further, by forming the light
guide member, the incident light adjusting member and the radiation light
adjusting member in a film shape, it is possible to realize the reduction
of thickness and the reduction of the weight of the planar light source
device. Accordingly, as in the case of the above-mentioned means (12),
with the use of the planar light source device having the any one of the
above-mentioned means (8) to means (11) as the backlight of the display
device, it is possible to realize the reduction of thickness and the
reduction of weight of the backlight and, at the same time, the
brightness uniformity of the display region can be enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] FIG. 1 is a schematic view showing the schematic constitution of a
display device of an embodiment 1 according to the present invention;

[0042] FIG. 2 is an enlarged schematic view of an essential part of FIG.
1;

[0043] FIG. 3 is a schematic view for explaining a modification of the
embodiment 1;

[0044] FIG. 4 is a schematic view showing the schematic constitution of a
backlight of an embodiment 2 according to the present invention;

[0045] FIG. 5 is a cross-sectional view taken along a line A-A' in FIG. 4;

[0046] FIG. 6 is a schematic view for explaining a modification of the
embodiment 2;

[0047]FIG. 7 is a schematic view for explaining a variation of the
embodiment 2;

[0048] FIG. 8 is a schematic view showing the schematic constitution of a
backlight of an embodiment 3 according to the present invention;

[0049]FIG. 9 is a cross-sectional view taken along a line B-B' in FIG. 8;

[0050]FIG. 10 is a schematic view for explaining a modification of the
embodiment 3;

[0051] FIG. 11 is a schematic view showing the schematic constitution of a
backlight of an embodiment 4 according to the present invention;

[0052] FIG. 12 is a cross-sectional view taken along a line C-C' in FIG.
11.

[0053] FIG. 13 is a cross-sectional view taken along a line D-D' in FIG.
11;

[0054] FIG. 14 is a schematic view for explaining a modification of the
embodiment 4;

[0055] FIG. 15 is a cross-sectional view taken along a line E-E' in FIG.
14;

[0056] FIG. 16 is a cross-sectional view taken along a line F-F' in FIG.
14;

[0057]FIG. 17 is a schematic view for explaining one of advantageous
effects of the backlight of the embodiment 4;

[0058] FIG. 18 is a schematic view showing a constitutional example of a
display device which uses a conventional general backlight for comparing
with the backlight of the embodiment 4;

[0059] FIG. 19 is a schematic view showing the schematic constitution of a
backlight of an embodiment 5 according to the present invention;

[0060]FIG. 20 is a cross-sectional view taken along a line G-G' in FIG.
19;

[0061] FIG. 21 is a schematic view for explaining a mounting method of an
incident-light adjusting member;

[0062] FIG. 22 is a schematic view for explaining the manner of operation
of the backlight of the embodiment 5;

[0063] FIG. 23 is a schematic view showing one example of a method for
adhering a spot light source and the incident-light adjusting member in
the embodiment 5;

[0064] FIG. 24 is a cross-sectional view taken along a line H-H' in FIG.
23;

[0065] FIG. 25 is a schematic view showing one example of the arrangement
of the backlight and the display panel of the embodiment 5;

[0066] FIG. 26 is a schematic view showing another example of the
arrangement of the backlight and the display panel of the embodiment 5;

[0067] FIG. 27 is a schematic view for explaining a first variation of the
embodiment 5;

[0068] FIG. 28 is a schematic view for explaining a second variation of
the embodiment 5;

[0069] FIG. 29 is a schematic view showing the schematic constitution of a
backlight of an embodiment 6 according to the present invention; and

[0070] FIG. 30 is a cross-sectional view taken along a line J-J' in

[0071] FIG. 29.

DETAILED DESCRIPTION OF THE INVENTION

[0072] Hereinafter, the present invention is explained in detail in
conjunction with embodiments by reference to drawings.

[0073] Here, with respect to the whole drawings for explaining the
embodiments, parts having the same functions are given the same symbols
and their repeated explanation is omitted.

[0075] The display device of this embodiment 1 includes, for example, as
shown in FIG. 1, the light radiation portion 201 of a backlight below the
display panel 1.

[0076] The display panel 1 may be any kind of display panel provided that
the display panel 1 allows light radiated from the light radiation
portion 201 of the backlight to pass therethrough and displays an image
(a video). As one example of the display panel 1, for example, a liquid
crystal display panel in which a liquid crystal material is sandwiched
between a pair of substrates may be named. Further, in the display panel
1, in general, as shown in FIG. 1, polarizer films 3A, 3B are adhered to
a surface of the display panel 1 on which light radiated from the
backlight is incident and a surface of the display panel 1 from which
light is radiated respectively.

[0077] The light radiation portion 201 of the backlight is, for example,
as shown in FIG. 1 and FIG. 2, integrally configured such that the light
guide member 201a is sandwiched between the light semi-transmissive
member 201b and the reflective member 201c. Here, the light
semi-transmissive member 201b is made of a material having a refractive
index smaller than a refractive index of the light guide member 201a.

[0078] Further, in the embodiment 1, the light guide member 201a, the
light semi-transmissive member 201b and the reflective member 201c are
respectively formed of a film-like member. Hereinafter, the light guide
member 201a is referred to as a light guide film, the light
semi-transmissive member 201b is referred to as a light semi-transmissive
film and the reflective member 201c is referred to as a reflective film.
Here, a thickness Ta of the light guide film 201a is set to 0.25 mm or
less, for example. Further, a thickness Tb of the light semi-transmissive
film 201b and a thickness Tc of the reflective film 201c are respectively
set to 0.05 mm or less, for example.

[0079] The light guide film 201a is made of polycarbonate (PC) having a
refractive index of 1.59, for example, while the light semi-transmissive
film 201b is made of fluororesin having a refractive index of 1.35, for
example. Here, the light semi-transmissive film 201b may be also made of
polyethylene terephthalate (PET) having a refractive index of 1.57 or an
acrylic UV curing resin having a refractive index of 1.49, for example.
Further, the reflective film 201c is formed of a polyester multi-layered
film or a silver sheet which is prepared by sputtering silver to a PET
substrate.

[0080] Further, in the embodiment 1, the light guide member 201a, the
light semi-transmissive member 201b and the reflective member 201c are
formed into the integral structure by adhering them to each other using
an optical adhesive agent having a refractive index which is
substantially equal to a refractive index of the light semi-transmissive
member 201b, for example.

[0081] In the display device having such a constitution, for example, as
shown in FIG. 1 and FIG. 2, light 4 is incident on the light radiation
portion 201 of the backlight from an end portion of a surface of the
light guide film 201a which faces the display panel 1 in an opposed
manner (hereinafter, referred to as a film surface). Then, the incident
light 4 is propagated in the inside of the light guide film while
repeating the reflection between an interface with the light
semi-transmissive film 201b and an interface with the reflective film
201c. Here, on the interface with the light semi-transmissive film 201b,
corresponding to the relationship between a refractive index of the light
guide film 201a and a refractive index of the light semi-transmissive
film 201b, light having a shallow angle, that is, light having a large
incident angle with respect to the light semi-transmissive film 201b is
reflected on the interface. On the other hand, light having a deep angle,
that is, light having a small incident angle with respect to the light
semi-transmissive film 201b is refracted on the interface and is radiated
in the direction toward the display panel 1. The light which is reflected
on the interface with the light semi-transmissive film 201b is reflected
on the interface with the reflective film 201c and, again, is incident on
the interface with the light semi-transmissive film 201b. By allowing the
light which propagates through the light guide film 201a to repeat this
operation, the light 4 incident on the light guide film 201a is converted
into a planar light and is radiated to the display panel 1.

[0082] Here, although not shown in FIG. 1 and FIG. 2, a light source of
the light 4 which is incident on the light guide film 201a may be
arranged at any position provided that the light 4 which is incident on
the light guide film 201a propagates in the direction toward a region
which is overlapped to the display panel 1 from the light incident
position.

[0083] In this manner, in the display device according to the embodiment
1, the thickness Ta of the light guide film 201a is set to 0.25 mm or
less and the thickness Tb of the light semi-transmissive film 201b and
the thickness Tc of the reflective film 201c are respectively set to 0.05
mm or less. Accordingly, a total thickness of the thickness Ta of the
light guide film 201a, the thickness Tb of the light semi-transmissive
film 201b and the thickness Tc of the reflective film 201c can be, as a
matter of course, set to a value larger than 0 and equal to or less than
0.35 mm. Further, by forming these films into the integral structure, the
light radiation portion 201 of the backlight can be made thin and
light-weighted.

[0084] Further, by forming the light guide film 201a, the light
semi-transmissive film 201b and the reflective film 201c into the
integral structure, it is possible to propagate the light 4 which is
incident on the light guide film 201a by repeating the reflection of the
light 4 with high efficiency on the interface with the light
semi-transmissive film 201b and the interface with the reflective film
201c. Accordingly, loss of light attributed to leaking of light on
respective interfaces, particularly, on the interface with the reflective
film 201c can be reduced and hence, it is possible to increase the
brightness of light which is radiated to the display panel 1.

[0085] FIG. 3 is a schematic view for explaining a modification of the
embodiment 1.

[0086] In the display device of the embodiment 1, by forming the light
guide film 201a, the light semi-transmissive film 201b and the reflective
film 201c into the integral structure, the light 4 which is incident on
the light guide film 201a is propagated while repeating the reflection of
light with high efficiency between the interface with the light
semi-transmissive film 201b and the interface with the reflective film
201c. Here, the light semi-transmissive film 201b is a member which
reflects or refracts the light (allows the light to pass through)
corresponding to an incident angle of the light which is propagated
through the light guide film 201a and is incident on the interface with
the light semi-transmissive film 201b. That is, on the interface between
the light guide film 201a and the light semi-transmissive film 201b, a
portion of the light which is incident on the interface is reflected and
is continuously propagated through the light guide film 201a and a
remaining portion of the light is radiated to the display panel 1.
Accordingly, the light radiation portion 201 of the backlight may be
formed of a film having a function equal to a function of the light
semi-transmissive film 201b in place of the light semi-transmissive film
201b. As a member which has the function equal to the function of the
light semi-transmissive film 201b, a polarization reflective film can be
named, for example.

[0087] The polarization reflective film is, for example, a member whose
polarization surface allows only a component of the light which is
directed in a certain direction to pass through and reflects remaining
components of the light. Accordingly, with the use of the polarization
reflective film in place of the light semi-transmissive film 201b, out of
the light which propagates through the light guide film 201a, only the
component which agrees with a transmission axis (a polarization axis) of
the polarization reflective film passes through the polarization
reflective film and is radiated to the display panel 1. Then, the
remaining components are reflected and continuously propagated through
the light guide film 201a. The light which is reflected on the interface
with the polarization reflective film 201b is reflected on the interface
with the reflective film 201c and, again, is incident on the interface
with the polarization reflective film 201b. By allowing the light which
propagates through the light guide film 201a to repeat the operation, the
light 4 which is incident on the light guide film 201a is converted into
a planar light and is radiated to the display panel 1.

[0088] Here, the light which is radiated to the display panel 1 from the
light guide film 201a after passing through the polarization reflective
film is a light whose polarization surface agrees with the transmission
axis of the polarization reflective film. Accordingly, in using the
polarization reflective film, for example, as shown in FIG. 3, when the
polarization reflective film 201d is adhered to a surface of the light
guide film 201a which faces the display panel 1 in an opposed manner, a
transmission axis AX1 of the polarization reflective film 201d is
directed in the same direction as a transmission axis AX2 of the
polarizer 3A which is adhered to a surface of the display panel 1 which
faces the light radiation portion 201 in an opposed manner. Due to such a
constitution, the polarization surface of the light which is radiated to
the display panel 1 from the light guide film 201a after passing through
the polarization reflective film 201d agrees with the transmission axis
AX2 of the polarizer 3A which is positioned in front of the display panel
1 and hence, the light is allowed to pass through the polarizer 3A and to
be incident on the display panel 1.

[0089] Further, by setting a thickness of the polarization reflective film
201d to 0.05 mm or less, for example, in the same manner as the light
semi-transmissive film 201b and by forming the polarization reflective
film 201d, the light guide film 201a and the reflective film 201c into
the integral structure, the light radiation portion 201 of the backlight
can be made thin and light-weighted.

[0090] Here, in FIG. 3, the transmission axis AX1 of the polarization
reflective film 201d is arranged parallel to a side of the light guide
film 201a on which the light is incident. However, provided that the
direction of the transmission axis AX1 agrees with the direction of the
transmission axis AX2 of the polarizer 3A which is adhered to the display
panel 1, the transmission axis AX1 may be directed in any direction.

Embodiment 2

[0091] FIG. 4 is a schematic view showing the schematic constitution of a
backlight of an embodiment 2 according to the present invention. Further,
FIG. 5 is a cross-sectional view taken along a line A-A' of FIG. 4.

[0092] In the embodiment 2, on the premise of the constitution of the
embodiment 1, a constitutional example of a light radiation portion 201
which can obtain the in-plane uniformity of the brightness (the light
quantity) of light radiated on the display panel 1 is explained.

[0093] Here, the light radiation portion 201 of the backlight is, for
example, as shown in FIG. 4 and FIG. 5, formed into the integral
structure by sandwiching the light guide film 201a between the light
semi-transmissive film 201b and the reflective film 201c. A thickness of
the light guide film 201a is set to 0.25 mm or less. Further, thicknesses
of the light semi-transmissive film 201b and the reflective film 201c are
respectively set to 0.05 mm or less, for example. Further, the light
guide film 201a, the light semi-transmissive film 201b and the reflective
film 201c are respectively made of materials explained in conjunction
with the embodiment 1. Further, the light guide film 201a, the light
semi-transmissive film 201b and the reflective film 201c are formed into
the integral structure by the method explained in conjunction with the
embodiment 1.

[0094] Further, in this embodiment 2, a plurality of through holes
(through holes) TH is formed in a plurality of portions of the
semi-transmissive film 201b. The through holes TH are formed by etching
the light semi-transmissive film 201b, for example.

[0095] Further, the through holes TH are, for example, as shown in FIG. 4,
formed in such a state that a plurality of rows in which a plurality of
through holes TH is arranged in parallel to a side of the light guide
film 201a on which a region L on which light is incident is formed is
arranged in the propagation direction of the light. Here, it is
preferable to set intervals G1, G2, G3, G4, G5, G6, G7 between the
respective through holes TH in a state that the remoter the interval from
the side of the light guide film 201a on which light is incident, the
smaller the interval becomes as shown in FIG. 4. Further, although the
number of rows of the through holes TH is eight in the example shown in
FIG. 4, it is needless to say that the number of rows may be other than
eight.

[0096] When these through holes TH are formed in the light
semi-transmissive film 201b, for example, as shown in FIG. 5, the light 4
which is incident on the light guide film 201a from a certain position of
the light guide film 201a propagates through the light guide film 201a
following a path indicated by a solid-line arrow. Here, the light which
is reflected on the reflective film 201c and is incident on the interface
with the light semi-transmissive film 201b is incident on a region where
the through holes TH are formed. The light which is incident on the
region where the through holes TH are formed is refracted and is radiated
into inner spaces formed in the through holes TH. Then, the light is
reflected or is refracted on side surfaces of the through holes TH and is
radiated in the direction where the display panel 1 is arranged. That is,
by forming the through holes TH, the light is irregularly reflected on
the side surfaces of the through holes TH and is radiated in the
direction where the display panel 1 is arranged. Accordingly, in
comparison with the case of the embodiment 1, the in-plane uniformity of
the brightness (light quantity) of the light radiated to the display
panel 1 is enhanced.

[0097] Further, the light which propagates through the light guide film
201a exhibits a large light quantity in a region closer to the side on
which the light is incident and the light quantity is gradually decreased
as the region is away from the side on which the light is incident.
Accordingly, as shown in FIG. 4, by increasing the distribution density
of the through holes TH in the region remote from the side on which the
light is incident thus facilitating the irregular reflection of the
light, the in-plane uniformity of brightness (light quantity) of the
light which is radiated to the display panel 1 is further enhanced.

[0098] FIG. 6 is a schematic view for explaining a modification of the
embodiment 2.

[0099] In the backlight of the embodiment 2, for example, when the light
source of the light 4 which is incident on the light guide film 201a is
formed of a plurality of spot light sources, for example, even in a
region closer to the side on which the light is incident, the light
quantity is decreased between two spot light sources in the side
direction. Accordingly, in the backlight which uses the plurality of spot
light sources, it is preferable to arrange the through holes TH of the
light semi-transmissive film 201b in a state as shown in FIG. 6, for
example.

[0100] FIG. 6 shows a case in which the spot light sources are arranged on
two regions L of the light guide film. With respect to a point that a
plurality of rows in which a plurality of through holes TH is arranged in
parallel with a side of the light guide film 201a on which light is
incident is arranged in the transmission direction of the light, the
constitution of the embodiment 2 is similar to the constitution of the
embodiment 1. Further, in a region closer to the side on which the light
is incident, spreading of light from the spot light source is
insufficient and hence, a region where the light quantity is small is
formed between the spot light sources. Accordingly, by providing more
plurality of through holes TH in the region to increase the distribution
density of the through holes TH, it is possible to further enhance the
in-plane uniformity of the brightness (light quantity) of light which is
incident on the display panel 1.

[0101] In this manner, in the backlight of the embodiment 2, even when the
spot light sources are used, it is possible to enhance the in-plane
uniformity of the brightness (light quantity) of the light radiated on
the display panel 1.

[0102]FIG. 7 is a schematic view for explaining a variation of the
embodiment 2.

[0103] The embodiment 2 is configured to enhance the in-plane uniformity
of light radiated on the display panel 1 with irregular reflection of
light which is radiated in the direction of the display panel 1 from the
light guide film 201a. Here, as an example of a method of reflecting
light irregularly, as shown in FIG. 4 or the like, an example which forms
the through holes TH in the light semi-transmissive film 201b is shown.
However, instead of forming the through holes TH in the light
semi-transmissive film 201b, for example, as shown in FIG. 7, it is
possible to obtain the similar advantageous effect by forming a pattern
which irregularly reflects the light (hereinafter referred to as an
irregular reflection pattern) RP on the interface between the light guide
film 201a and the reflective film 201c.

[0104] When such an irregular reflection pattern RP is formed on the
interface between the light guide film 201a and the reflective film 201c,
for example, as shown in FIG. 7, the light 4 which is incident from a
certain position of the light guide film 201a propagates through the
light guide film 201a following a path indicated by a solid-line arrow.
Here, the light reflected on the irregular reflection pattern RP of the
reflective film 201c changes the path and the incident angle to the
interface with the light semi-transmissive film 201b is changed before
and after the light is reflected on the irregular reflection pattern RP.
Here, the incident angle of the light is decreased after the light is
reflected on the irregular reflection pattern. When the light is incident
at a deep angle, a portion of the light is refracted with the interface
with the light semi-transmissive film 201b and radiated in the direction
where the display panel 1 is arranged. Accordingly, in the same manner as
the case in which the through holes TH are formed in the light
semi-transmissive film, the in-plane uniformity of the brightness (light
quantity) of the light radiated to the display panel 1 is enhanced.

[0105] Further, here, the light guide film 201a and the reflective film
201c have the integral structure by being adhered using a transparent
optical adhesive agent, for example, and there is no gap on the
interface. Accordingly, it is possible to prevent the increase of the
loss of light due to the leaking of light from the interface between the
light guide film 201a and the reflective film 201c.

[0106] Here, when the irregular reflection pattern RP is formed at the
interface between the light guide film 201a and the reflective film 201c,
the irregular reflection pattern RP may be arranged, in the same manner
as the arrangement of the through holes TH in the light semi-transmissive
film 201b shown in FIG. 4 or FIG. 6, in a state that the distribution
density is higher in a region remoter from the side of the light guide
film 201a on which light is incident or in a region between the spot
light sources.

[0107] Further, although, in the embodiment 2, the explanation is made
with respect to the example in which the light semi-transmissive film
201b is used, it is needless to say that the polarization reflective film
201d may be used in place of the light semi-transmissive film 201b.

[0108] Further, although, in the embodiment 2, for example, as shown in
FIG. 4, the through holes TH are arranged in a row, it is needless to say
that the through holes TH may be arranged at arbitrary positions.

Embodiment 3

[0109] FIG. 8 is a schematic view showing the schematic constitution of a
backlight of an embodiment 3 according to the present invention. Further,
FIG. 9 is a cross-sectional view taken along a line B-B' in FIG. 8.

[0110] In the embodiment 3, a constitutional example of the light
radiation portion 201 which enables the in-plane uniformity of the
brightness (light quantity) of the light radiated on the display panel 1
on the premise of the constitution of the embodiment 1 and in a method
different from the embodiment 2 is explained.

[0111] Here, the light radiation portion 201 of the backlight is, as shown
in FIG. 8 and FIG. 9, formed in the integral structure by sandwiching the
light guide film 201a between the light semi-transmissive film 201b and
the reflective film 201c. The thickness of the light guide film 201a is
set to 0.25 mm and less. Further, the thicknesses of the light
semi-transmissive film 201b and the reflective film 201c are respectively
set to 0.05 mm or less. Further, the light guide film 201a, the light
semi-transmissive film 201b and the reflective film 201c are made of the
materials which are explained in the embodiment 1. Further, the light
guide film 201a, the light semi-transmissive film 201b and the reflective
film 201c are formed in the integral structure in such a manner which is
explained in conjunction with the embodiment 1.

[0112] Further, in the case of embodiment 3, the light semi-transmissive
film 201b is provided with a pattern which blocks light on a plurality of
portions (hereinafter, referred to as a light blocking pattern) BP. This
light blocking pattern BP is, for example, formed by printing the white
ink or the like.

[0113] Further, the light blocking patterns BP are, for example, as shown
in FIG. 8, formed in such a state that a plurality of rows in which a
plurality of light blocking patterns BP is arranged in parallel to a side
of the light guide film 201a on which a region L on which light is
incident is formed is arranged in the transmission direction of the
light. Here, as shown in FIG. 8 it is preferable to set intervals between
the respective light blocking patterns BP G1, G2, G3, G4, G5, G6, G7 in a
state that the remoter the interval from the side of the light guide film
201a on which the light is incident, the smaller the gap becomes.
Further, although the number of rows of the light blocking patterns BP is
eight in an example shown in FIG. 8, it is needless to say that the
number may be other than eight.

[0114] When the light blocking patterns BP are provided to the light
semi-transmissive film 201b, for example, as shown in FIG. 9, the light 4
which is incident from a certain position of the light guide film 201a
propagates through the light guide film 201a following a path indicated
by a solid-line arrow. Here, the light which is reflected on the
reflective film 201c and is incident on the interface with the light
semi-transmissive film 201b is blocked (reflected) with the light
blocking patterns BP and hence, the light is not radiated in the
direction where the display panel is arranged after propagating through
the light transmissive film 201b. That is, by providing the light
blocking patterns BP, it is possible to limit the light quantity of the
light radiated in the direction where the display panel 1 is arranged.
Accordingly, compared to the case of the embodiment 1, the in-plane
uniformity of the brightness (light quantity) of the light radiated on
the display panel 1 is enhanced.

[0115] Further, here, the light which propagates through the light guide
film 201a exhibits a large light quantity in a region closer to the side
on which the light is incident and the light quantity is gradually
decreased as the region recedes from the side on which the light is
incident. Accordingly, as shown in FIG. 8, by increasing the distribution
density of the light blocking patterns BP in the region close to the side
on which the light is incident and by decreasing the light quantity of
the light radiated in the direction where the display panel 1 is
arranged, the in-plane uniformity of the brightness (light quantity) of
the light radiated on the display panel is further enhanced.

[0116]FIG. 10 is a schematic view for explaining a modification of the
embodiment 3.

[0117] In the backlight of the embodiment 3, for example, when the light
source of the light 4 which is incident on the light guide film 201a is
formed of a plurality of spot light sources, for example, even in the
region closer to the side on which the light is incident, the light
quantity is decreased between two spot light sources in the side
direction. Accordingly, in the backlight which uses the plurality of
light sources, it is preferable to arrange the light blocking patterns BP
in a state as shown in FIG. 10, for example.

[0118]FIG. 10 shows a case in which the spot light sources are arranged
on two regions L of the light guide film 201a. With respect to a point
that a plurality of rows in which a plurality of light blocking patterns
BP is arranged in parallel to a side of the light guide film 201a on
which the light is incident is arranged in the propagating direction of
the light, the constitution of the embodiment 3 is similar to the
constitution of the embodiment 1. Further, in a region closer to the side
on which the light is incident, spreading of light from the spot light
source is insufficient and hence, a region where the light quantity is
small is formed between the spot light sources. Accordingly, by
increasing the distribution density of the light blocking pattern in the
region immediately front of the spot light source where the light
quantity is large in the region close to the side where the light is
incident, it is possible to further enhance the in-plane uniformity of
the brightness (light quantity) of light which is incident on the display
panel 1.

[0119] In this manner, in the backlight of the embodiment 3, even when the
spot light sources are used, it is possible to enhance the in-plane
uniformity of the brightness (light quantity) of the light radiated on
the display panel.

[0120] Further, although, in the embodiment 3, the explanation is made
with respect to the example in which the light semi-transmissive film
201b is used, it is needless to say that the polarization reflective film
201d may be used in place of the light semi-transmissive film 201b.

[0121] Further, although, in the embodiment 3, for example, as shown in
FIG. 8, the light blocking patterns BP are arranged in a row, it is
needless to say that the light blocking patterns BP may be arranged at
arbitrary positions.

Embodiment 4

[0122] FIG. 11 is a schematic view showing the schematic constitution of
the backlight of the embodiment 4 according to the present invention.
Further, FIG. 12 is a cross-sectional view taken along a line C-C' in
FIG. 11. Further, FIG. 13 is a cross-sectional view taken along a line
D-D' in FIG. 11. Here, FIG. 11 shows a front view of the backlight and a
side view of the lower side of the backlight.

[0123] In the embodiment 4, on the premise of the constitution of the
light radiation portion 201 of the backlight which is explained in
conjunction with the embodiment 1 to the embodiment 3, a constitutional
example of a backlight including a light source of light which is
incident on the light guide film 201a.

[0124] Here, the light radiation portion 201 of the backlight is, as shown
in FIG. 11 to FIG. 13, formed in the integral structure by sandwiching
the light guide film 201a between the light semi-transmissive film 201b
and the reflective film 201c. The thickness of the light guide film 201a
is set to 0.25 mm or less. Further, the thicknesses of the light
semi-transmissive film 201b and the reflective film 201c are respectively
set to 0.05 mm or less, for example. Further, the light guide film 201a,
the light semi-transmissive film 201 band the reflective film 201c are
respectively made of materials explained in conjunction with the
embodiment 1. Further, the light guide film 201a, the light
semi-transmissive film 201b and the reflective film 201c are formed in
the integral structure in such a manner which is explained in conjunction
with the embodiment 1.

[0125] Further, here, the light radiation portion 201 may have, for
example, through holes TH formed in the light semi-transmissive film 201b
at a plurality of positions in the same manner as the embodiment 2.
Further, in place of the through holes TH, for example, an irregular
reflection pattern RP may be provided with the interface between the
light guide film 201a and the reflective film 201c. Further, for example,
in the same manner as the embodiment 3, light blocking patterns BP may be
provided with the interface between the light semi-transmissive film 201b
and the light guide film 201a.

[0126] A light source of light 4 which is incident on the light guide film
201a is formed of a spot light source 202 such as an LED, for example.
The spot light sources 202 are mounted on a flexible circuit board 203,
for example. Here, the flexible circuit board 203 on which the spot light
sources 202 are mounted is arranged on, for example, on the light
semi-transmissive film 201b of the light radiation portion 201, and
outside a region where the light is radiated to a display region of the
display panel 1 (hereinafter referred to as a radiation region) IR.
Further, the spot light sources 202 on the flexible circuit board 203 use
a side-view-type LED, for example, and are mounted in a state that the
light is radiated in the film surface direction of the light guide film
201a and in the direction opposite to radiation region IR.

[0127] Further, here, a reflector 204 is provided to an end portion of the
light guide film 201a on a side on which the spot light sources 202 are
arranged. The light 4 which is radiated from the spot light source 202
is, as shown in FIG. 14 and FIG. 15, reflected on a reflective surface
204a of the reflector 204 and changes the direction thereof to the
radiation region IR and, thereafter, is incident on the light guide film
201a. The manner in which the incident light 4 propagates through the
light guide film 201a is the same manner as explained in conjunction with
the embodiments 1 to 3 and hence, the detailed explanation is omitted.

[0128] Here, in the embodiment 4, the spot light source 202 such as LED is
used as the spot light source, and this LED is usually configured such
that the spreading of radiated light 4 is small to enhance the
brightness. Accordingly, out of the reflective surfaces 204a of the
reflection plate 204, by forming the surface which faces the light
radiation surface of the spot light source 202 in an opposed manner, for
example, to project to the spot light source 202 side as shown in FIG.
13, it is possible to spread the light of the spot light source 202. Due
to such a constitution, it is possible to effectively propagate the light
to a region between two spot light sources 202.

[0129] FIG. 14A and FIG. 14B are schematic views for explaining a
modification of the embodiment 4, wherein FIG. 14A is a front view of a
backlight and FIG. 14B is a side view of a lower portion of the
backlight. Further, FIG. 15 is a cross-sectional view taken along a line
E-E' in FIG. 14A, and FIG. 16 is a cross-sectional view taken along a
line F-F' in FIG. 14B.

[0130] The backlight of the embodiment 4 uses the spot light source 202
formed of a side-view-type LED, wherein light radiated toward the film
surface of a light guide film 201a from the spot light source 202 is
reflected on the reflector 204 and is incident on the light guide film
201a. Here, for example, as shown in FIG. 13, by forming a reflection
surface 204a which forms a convex curved surface on a
spot-light-source-202 side of the reflector 204, the light radiated from
the spot light source 202 can be spread. However, this embodiment is not
limited to the reflective surface 204a having the convex curved surface
shown in FIG. 13 and, it is possible to spread the light radiated from
the spot light source 202 by also using a reflective surface 204b which
projects toward the spot-light-source-202 side by combining planar
surfaces shown in FIG. 14 to FIG. 16, for example.

[0131]FIG. 17 is a schematic view for explaining one advantageous effect
of the backlight of the embodiment 4. Further, FIG. 18 is a schematic
view showing a constitutional example of a display device which uses a
conventional general backlight for comparison with the backlight of the
embodiment 4.

[0132] The backlight of the embodiment 4 is integrally constituted of the
light guide film 201a, the light semi-transmissive film 201b and the
reflective film 201c thus reducing a thickness of the light radiation
portion 201. Further, the spot light source 202 of the light which is
incident on the light guide film 201a is formed on the light guide film
201a, and is arranged outside a radiation region IR which radiates the
light to the display panel 1. Accordingly, in the display device which
uses the backlight of the embodiment 4, for example, as shown in FIG. 17,
it is possible to arrange the spot light source 202 and the reflector 204
in the direction toward the side surface of the display panel 1. Due to
such a constitution, it is possible to absorb an amount of thickness
corresponding to a height of the flexible printed circuit board 203 and
the height of the mounted spot light source 202 which is arranged over
the light semi-transmissive film 201b and hence, a thickness Td of the
structure obtained by overlapping the display panel 1 and the backlight
(the light radiation portion 201) to each other can be reduced.

[0133] The conventional display device uses the light guide plate formed
by injection molding, for example, and the spot light source 202 is
arranged on a side surface of the light guide plate 201e as shown in FIG.
18. By providing such a constitution to the backlight, the thickness of
the light guide plate 201e becomes approximately 0.4 mm, for example.
Accordingly, a thickness Te of the structure obtained by overlapping the
display panel 1 and the backlight (the light radiation portion 201) to
each other becomes approximately 1.06 mm, for example.

[0134] On the other hand, in case of the display device which uses the
backlight of the embodiment 4, the thickness of the light radiation
portion 201 of the backlight becomes 0.35 mm or less. Accordingly, the
thickness Td of the structure obtained by overlapping the display panel 1
and the backlight (the light radiation portion 201) to each other becomes
approximately 0.95 mm.

[0135] In view of the above, with the use of the backlight of the
embodiment 4, the display device can be made thin and light-weighted, and
the in-plane uniformity of a light quantity of the radiation region IR is
enhanced.

[0136] Here, in this embodiment 4, a case which uses the light
semi-transmissive film 201b is exemplified. However, it is needless to
say that a polarization reflective film 201d may be used in place of the
light semi-transmissive film 201b.

Embodiment 5

[0137] FIG. 19 is a schematic view showing the schematic constitution of a
backlight of an embodiment 5 according to the present invention, FIG. 20
is a cross-sectional view taken along a line G-G' in FIG. 19, and FIG. 21
is a schematic view for explaining a mounting method of an incident-light
adjusting member.

[0138] In the embodiment 5, on the premise of the constitution of the
light radiation portion 201 of the backlight explained in conjunction
with the embodiment 1 to embodiment 3, another constitutional example of
the backlight which includes the light source of light incident on the
light guide film 201a is explained.

[0139] Here, the light radiation portion 201 of the backlight is, as shown
in FIG. 19 and FIG. 20, formed into the integral structure in which the
light guide film 201a is sandwiched between the light semi-transmissive
film 201b and a reflective film 201c. A thickness of the light guide film
201a is set to 0.25 mm or less. Further, thicknesses of the light
semi-transmissive film 201b and the reflective film 201c are respectively
set to 0.05 mm or less, for example. Further, the light guide film 201a,
the light semi-transmissive film 201b and the reflective film 201c are
respectively made of the material which has been explained in conjunction
with the embodiment 1, for example. Further, the light guide film 201a,
the light semi-transmissive film 201b and the reflective film 201c are
formed into the integral structure using the method explained in
conjunction with the embodiment 1.

[0140] Further, in the light radiation portion 201, through holes TH may
be formed in a plurality of portions of the light semi-transmissive film
201b as in the case of the embodiment 2, for example. Further, in place
of the through holes TH, an irregular reflection pattern RP may be
provided to an interface between the light guide film 201a and the
reflective film 201c. Still further, for example, as in the case of the
embodiment 3, a light blocking pattern BP may be provided to an interface
between the light semi-transmissive film 201b and the light guide film
201a.

[0141] Further, a light source of light 4 which is incident on the light
guide film 201a may be a spot light source 202 formed of an LED, for
example. The spot light source 202 may be mounted on the flexible printed
circuit board 203, for example. Here, the flexible printed circuit board
203 on which the spot light source 202 is mounted is arranged on a side
of the light radiation portion 201 (the light guide film 201a) to which
the reflective film 201c is provided, for example and, at the same time,
outside a radiation region IR which radiates light to a display region of
a display panel 1. Here, the spot light source 202 on the flexible
printed circuit board 203 is formed of a top-view type LED, for example,
and is mounted so as to radiate light in the direction perpendicular to
the film-surface direction of the light guide film 201a.

[0142] Here, between the light guide film 201a and the spot light source
202, an incident-light adjusting member 205 which forms a plurality of
projections 205a on a surface thereof which faces the light guide film
201a in an opposed manner is interposed. The incident-light adjusting
member 205 is made of a material equal to a material of the light guide
film 201a. Further, the incident-light adjusting member 205 has a distal
end of the projection 205a thereof formed in a flat surface shape and is
brought into close contact with a film surface of the light guide film
201a.

[0143] The incident-light adjusting member 205 may preferably be formed of
a film having a thickness of 0.1 mm to 0.2 mm including the projections
205a, for example. Further, the projections 205a may be formed by
photolithography, for example.

[0144] Further, distal end surfaces of the projections 205a of the
incident-light adjusting member 205 may be brought into close contact
with the light guide film 201a by, for example, as shown in FIG. 21,
applying an optical adhesive agent 206 to the distal end surfaces of the
projections 205a and adhering the distal end surfaces of the projections
205a on the film surfaces of the light guide film 201a.

[0145] Further, the projections 205a of the incident-light adjusting
member 205 may be formed of columnar projections having curved bottom
surfaces as shown in FIG. 19, for example. Further, the projections 205a
of the incident-light adjusting member 205 may, for example, as shown in
FIG. 20, have side surfaces thereof on a side opposite to the radiation
region IR formed into a convex curved shape. Further, in the backlight
shown in the embodiment 5, it is preferable to provide a reflective sheet
207 which is overlapped to the incident-light adjusting member 205 to a
surface of the light guide film 201a to which the light semi-transmissive
film 201b is provided.

[0146] FIG. 22 is a schematic view for explaining the manner of operation
of the backlight of the embodiment 5.

[0147] The manner of operation of the backlight of the embodiment 5 is
explained in conjunction with FIG. 22. Here, FIG. 22 is an enlarged
cross-sectional view of a region AR1 shown in FIG. 20.

[0148] In the backlight of the embodiment 5, a spot light source 202 such
as the LED is, as shown in FIG. 20, arranged such that the spot light
source 202 radiates light in the direction perpendicular to the film
surface of the light guide film 201a. Accordingly, in such a state, a
light from the spot light source 202 exhibits a small incident angle with
respect to the light guide film 201a and hence, it is impossible to make
the incident light 4 propagate into the radiation region IR. Accordingly,
between the spot light source 202 and the light guide film 201a, the
incident-light adjusting member 205 having the projections 205a shown in
FIG. 22 is interposed. Here, the light 4 which is radiated in the
direction perpendicular to the film surface of the light guide film 201a
is, for example, as shown in FIG. 22, reflected on the convex curved
surfaces of the projections 205a of the incident-light adjusting member
205 on a side opposite to the radiation region IR thus changing an
advancing path thereof and, thereafter, the light 4 is incident on the
light guide film 201a. The manner in which the incident light propagates
through the light guide film 201a is exactly as same as the manner of
propagation of the incident light explained in conjunction with the
embodiment 1 to embodiment 3 and hence, the detailed explanation is
omitted.

[0149] Here, the convex curved surface of the projection 205a of the
incident-light adjusting member 205 adopts a shape which allows a
reflection angle θ of the light on the convex curved shape to
satisfy a following formula (1).

θ=i/2>(arcsin(1/n))/2 (1)

[0150] Here, in the formula (1), "i" indicates an incident angle of the
light on the interface between the light guide film 201a and the light
semi-transmissive film 201b, and "n" indicates a refractive index of the
incident-light adjusting member 205 and the light guide film 201a.

[0151] The light which is radiated from the spot light source 202 such as
the LED exhibits the largest component in the direction perpendicular to
the film surface of the light guide film 201a. However, by forming the
light components other than the light component in the perpendicular
direction to have the shape which satisfies the formula (1), it is
possible to allow such light components to be effectively incident on the
light guide film 201a.

[0152] Further, for example, among the light which is radiated in the
direction perpendicular to the film surface of the light guide film 201a,
there exists light which passes through a portion different from the
convex curved shape of the projection 205a. In this case, the light is
incident perpendicular to the film surface of the light guide film 201a
and hence, the light is not reflected on the interface with the light
semi-transmissive film 201b whereby the light passes through the light
semi-transmissive film 201b. Accordingly, by providing a reflective sheet
207 to a region on the light semi-transmissive film 201b which is
overlapped to the incident-light adjusting member 205, the light which
passes through the light semi-transmissive film 201b is reflected on the
reflective sheet 207 thus allowing the incidence of the light on the
light guide film 201a again.

[0153] FIG. 23 is a schematic view showing one example of a method for
adhering the spot light source and the incident-light adjusting member
205 in the embodiment 5. Further, FIG. 24 is a cross-sectional view taken
along a line H-H' in FIG. 23.

[0154] In the backlight of the embodiment 5, it is preferable to adhere
the spot light source 202 such as the LED to the incident-light adjusting
member 205 using an annular adhesive agent 208 as shown in FIG. 23 and
FIG. 24, for example. Here, the annular adhesive agent 208 may be
provided to an outermost periphery of a light radiation surface of the
spot light source 202 for preventing the blocking of light from the light
emitting element (LED chip) 202a which the spot light source 202
possesses.

[0155] FIG. 25 is a schematic view showing one example of the arrangement
of the backlight and the display panel of the embodiment 5. Further, FIG.
26 is a schematic view showing another example of the arrangement of the
backlight and the display panel of the embodiment 5.

[0156] In the backlight of the embodiment 5, for example, as shown in FIG.
20, the incident-light adjusting member 205 and the spot light source 202
are arranged on a surface side of the light guide film 201a on which the
reflective film 201c is arranged. Here, the display panel 1 is arranged
on a surface side of the light guide film 201a to which the light
semi-transmissive film 201b is provided. Accordingly, as shown in FIG.
25, the spot light source 202 is arranged on the back surface of the
light radiation portion 201 of the backlight.

[0157] By adopting such an arrangement, for example, it is also possible
to arrange the incident-light adjusting member 205 such that the
incident-light adjusting member 205 is overlapped to the display panel 1
partially or as a whole. Accordingly, a region of the display device
outside the display region, so-called a picture frame region can be made
small.

[0158] Here, in the backlight of the embodiment 5, the spot light source
202 and the incident-light adjusting member 205 may be, for example, as
shown in FIG. 26, arranged on a surface side of the light guide film 201a
to which the light semi-transmissive film 201b is provided.

[0159] FIG. 27 is a schematic view for explaining a first variation of the
embodiment 5.

[0160] In explaining the constitution of the backlight of the embodiment
5, the case in which one spot light source 202 is arranged is exemplified
as shown in FIG. 19, for example. However, the present invention is not
limited to such backlight constitution and, for example, two spot light
sources 202 may be arranged as shown in FIG. 27. Further, although not
shown in the drawing, it is needless to say that three or more spot light
sources 202 may be arranged.

[0161] FIG. 28 is a schematic view for explaining a second variation of
the embodiment 5.

[0162] In explaining the constitution of the backlight of the embodiment
5, for example, as shown in FIG. 20, the case in which the reflective
sheet 207 which is overlapped to the incident-light adjusting member 205
is adhered to the light semi-transmissive film 201b is exemplified.
However, the present invention is not limited to the backlight
constitution and, for example, as shown in FIG. 28, a prism sheet 209 may
be arranged between the light semi-transmissive film 201b and the
reflective sheet 207. By arranging the prism sheet 209 in such a manner,
light which is reflected on the reflective sheet 207 after passing
through the light semi-transmissive film 201b is allowed to be incident
on the light guide film 201a again by setting a certain incident angle
thus further enhancing the utilization efficiency of the light.

[0163] Further, although the explanation using drawings may be omitted, it
is needless to say that the arrangement of the plurality of projections
205a of the incident-light adjusting member 205 is not limited to the
arrangement in a matrix array as shown in FIG. 19, for example. With
respect to the arrangement of the projections, it may be possible to
adopt a method in which a plurality of projections 205a are arranged on
curved lines which project in the direction toward the radiation region
IR such as concentric circumferences about a certain point, for example.

Embodiment 6

[0164] FIG. 29 is a schematic view showing the schematic constitution of a
backlight of an embodiment 6 according to the present invention. Further,
FIG. 30 is a cross-sectional view taken along a line J-J' in FIG. 29.

[0165] The backlight of the embodiment 6 is a backlight of another
modification of the embodiment 5, wherein the constitution of the light
source 202 and the vicinity of the light source 202 is equal to the
corresponding constitution of the backlight of the embodiment 5. A point
which makes this embodiment 6 different from 5 lies in the constitution
of the radiation region IR of the light guide film 201a.

[0166] In the backlight of this embodiment 6, for example, as shown in
FIG. 29 and FIG. 30, to a film surface of a light guide film 201a, a
light semi-transmissive member 201b or a polarization reflective film
201d, and a reflective film 201c are not adhered. In place of such a
constitution, a radiation-light adjusting member 201f is provided to one
film surface of the light guide film 201a, that is, the surface of the
light guide film 201a which faces the display panel 1 in an opposed
manner. The radiation-light adjusting member 201f is a member which
adjusts a radiation angle of the light which is radiated from the film
surface of the light guide film 201a and is radiated to the display panel
1.

[0167] Further, the radiation-light adjusting member 201f has
substantially the same constitution as the incident-light adjusting
member 205, for example, wherein the radiation-light adjusting member
201f has one, two or more projections on a surface thereof which faces
the light guide film 201a in an opposed manner, and distal-end surfaces
of the projections are brought into contact with a film surface of the
light guide film 201a. Here, although the projections are arranged only
in a region close to the light source 202, in an actual arrangement, the
projections similar to the projections shown in FIG. 29 and FIG. 30 are
arranged over the whole region of the radiation-light adjusting member
201f. Here, the radiation-light adjusting member 201f may preferably be
formed of a film having a thickness of 0.05 mm including the projections,
for example. Further, the projections may be formed by photolithography,
for example.

[0168] Further, distal end surfaces of the projections of the
radiation-light adjusting member 201f may be brought into close contact
with the light guide film 201a by, for example, applying an optical
adhesive agent to the distal end surfaces of the projections and adhering
the distal end surfaces of the projections on the film surfaces of the
light guide film 201a.

[0169] Further, the projections of the radiation-light adjusting member
201f may be formed of columnar projections having curved bottom surfaces
as shown in FIG. 29, for example. Further, the projections of the
radiation-light adjusting member 201f may, for example, as shown in FIG.
30, have side surfaces thereof on a side opposite to the light source 202
formed into a convex curved shape.

[0170] Here, also in the backlight of the embodiment 6, a thickness of the
light guide film 201a is set to 0.25 mm or less. Further, the light guide
film 201a may be made of polycarbonate (PC) having a refractive index of
1.59.

[0171] The backlight of the embodiment 6 does not use the light
semi-transmissive film 201b or the polarization reflective film 201d and
the reflective member 201c. However, the refractive index of the light
guide film 201a is larger than the refractive index of air and hence, the
light 4 which is incident on the light guide film 201a after passing
through the incident-light adjusting member 205 repeats the total
reflection on the film surface, that is, on an interface between the
light guide film 201a and air and propagates in the inside of the light
guide film 201a.

[0172] Here, at portions where the projections of the radiation-light
adjusting member 201f and the light guide film 201a are brought into
contact with each other, the refractive index is substantially equal and
hence, no total reflection occurs whereby the light 4 advances to the
inside of the projections of the radiation-light adjusting member 201f
directly. Then, the light 4 which enters the inside of the projections
are reflected on the interfaces between the side surfaces of the
projections and air and, thereafter, is radiated in the direction toward
the display panel 1.

[0173] In this manner, according to the backlight of the embodiment 6,
with the use of the radiation-light adjusting member 201f in place of the
light semi-transmissive film 201b or the polarization reflective film
201d and the reflective film 201c, it is possible to obtain the
advantageous effects substantially equal to the advantageous effects
obtained by the backlight of the embodiment 5. Accordingly, it is
possible to decrease kinds of sheets (films) which are adhered to the
light guide film 201a and hence, the light guide film 201a can reduce the
thickness thereof thus realizing the backlight at a low cost.

[0174] Although the present invention has been specifically explained in
conjunction with the embodiments, it is needless to say that the present
invention is not limited to the above-mentioned embodiments and various
modifications are conceivable without departing from the gist of the
present invention.

[0175] The backlights which have been explained in conjunction with
respective embodiments are thin and light-weighted and, at the same time,
exhibit high brightness uniformity of the radiation surface. Accordingly,
the constitutions of the backlights which are exemplified in the
respective embodiments may not be limited to the light source of the
display device such as the liquid crystal display device and may be
applicable to a planar light source device (unit) such as illumination
equipment, for example.

Patent applications by Hiroshi Kurihara, Mobara JP

Patent applications in class With integral optical element for guiding or distributing light from the light source

Patent applications in all subclasses With integral optical element for guiding or distributing light from the light source